Sonic signal generator and housing

ABSTRACT

A sonic signal generator utilizing a substantial amount of the surface area of a nodally mounted transducer for the generation of sound. A conventional piezoelectric ceramic crystal is affixed to a thin brass disk, forming a transducer. The transducer is nodally mounted; that is, attached to a mounting member along a transducer surface path which does not move when the transducer is excited. When the transducer is electronically excited, sound in the form of acoustic waves emanating from selected surface areas of the transducer is directed by means of a novel ported structure surrounding the transducer such that selected sound having a given phase is combined and directed through a first series of ports, while selected sound having the opposite phase may be directed through a second series of ports, the radial centers of which are substantially 90* removed from the radial centers of the first series of ports. This configuration results in a minimum of acoustic wave cancellation and thus a significant increase in transducer efficiency for a given power input.

United States Patent [191 Livermore et al.

[ Nov. 18, 1975 1 SONIC SIGNAL GENERATOR AND HOUSING [73] Assignee: Proctor & Associates Company,

- Redmond, Wash.

[22] Filed: Dec. 12, 1973 [21] Appl. No.: 424,162

[52] U.S. Cl 3l0/9.l; 179/110 A; 179/121 B;

310/82; 310/85, 340/8 PT [51] Int. Cl. H01L 41/04 [58] Field of Search 310/8.2, 8.3, 8.5, 8.6,

310/87, 8.8, 9.1, 9.4, 8.1; 346/405, 406, 388, 391; 181/31 A, 31 B, 31 R, 32, 33 E; 179/110 A, 121 D, 1 E

[56] References Cited UNITED STATES PATENTS 2,787,671 4/1957 Grosskopf et a1 179/121 D 3,331,970 1/1968 Dundon et a1. 310/9.l 3,536,862 10/1970 Weingartner 179/121 D 3.560.668 2/1971 Warning 181/31 A 3,739,096 6/1973 Iding 179/1 E 3,754,435 8/1973 Zeutschel 310/8.7 X 3,761,956 9/1973 Takahashi et a1 310/82 3,860,838 l/1975 Kumon 310/82 X 3,872,470 3/1975 Hoerz 310/82 X 3,873,866 3/1975 Goble 310/82 FOREIGN PATENTS OR APPLICATIONS 29.444 9/1956 Germany 181/31 B Primary E.raminerMark O. Budd Attorney, Agent, or FirmChristensen, OConnor, Garrison & Havelka [57] ABSTRACT A sonic signal generator utilizing a substantial amount of the surface area of a nodally mounted transducer for the generation of sound. A conventional piezoelectric ceramic crystal is affixed to a thin brass disk, forming a transducer. The transducer is nodally mounted; that is, attached to a mounting member along a transducer surface path which does not move when the transducer is excited. When the transducer is electronically excited, sound in the form of acoustic waves emanating from selected surface areas of the transducer is directed by means of a novel ported structure surrounding the transducer such that selected sound having a given phase is combined and directed through a first series of ports, while selected sound having the opposite phase may be directed through a second series of ports, the radial centers of which are substantially 90 removed from the radial centers of the first series of ports. This configuration results in a minimum of acoustic wave cancellation and thus a significant increase in transducer efficiency for a given power input.

30 Claims, 11 Drawing Figures Sheet 1 of6 US. Patent Nov. 18, 1975' Sheet 2 of 6 3,921,016

US. Patent Nov. 18, 1975 U.S. Patent Nov. 18,1975 Sheet30f6 3,921,016

US. Patent Nov. 18, 1975 Sheet4of6 3,921,016

U.S. Patent N0v.18,1975 Sheet50f6 3,921,016

US. Patent Nov. 18, 1975 Sheet6of6 3,921,016

SONIC SIGNAL GENERATOR AND HOUSING BACKGROUND OF THE INVENTION This invention relates generally to the art of sonic signal generators, and more specifically, to the art of sonic signal generators using a piezoelectric transducer.

Many types of sonic ringing devices are currently available. These devices typically provide an audible alarm upon being energized, such as the mechanical bell device now present in most telephone sets. Such ringing devices can be divided into two basic categories, one category using mechanical or electromechanical principles, e.g., the telephone bell, the other category using electronic principles, e.g., crystal controlled sonic signal generators.

Significant disadvantages to the mechanical approach include high power requirements, substantial size, weight, and lack of long term reliability. Sonic transducers, on the other hand, have had a disadvantage in that although they are more efficient than a bell they havenot been utilized efficiently since less than one-quarter of the transducer surface area has heretofore. been used for sound production. The remaining surface areas of the transducer are damped, so as to prevent resulting acoustic wave cancellation. This cancellation is caused by the out-of-phase wavefronts of the generated acoustic waves emanating from the crystal transducer impinging on each other. Such a damped transducer is disclosed in US. Pat. No. 3,331,970 to Dundon et al. To overcome these disadvantages of conventional mechanical and electronic audible alarm de vices, the present invention combines a novel signal generator structure with a nodally mounted crystal transducer to provide a sonic generator having power and size advantages over mechanical devices, and significant increase in sonic efficiency over conventional cyrstal transducer generators. In accordance with the above, it is a general object of the present invention to provide a sonic signal generator which overcomes the disadvantages of the prior art.

It is another object of the present invention to provide a sonic signal generator wherein more surface area of a transducer is used for sound production than here tofore.-

It is another object of the present invention to provide a sonic signal generator having a greater sound efficiency than the prior art.

It is a further object of the present invention to provide a sonic signal generator having minimum space and power requirements.

It is yet another object of the present invention to provide a sonic signal generator which is compatible with conventional telephone receivers.

7 SUMMARY OF THEINVENTION moved from said selected port, thus reducing wavefront interference between the acoustic waves.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of the present invention fully assembled.

FIG. 2 is an exploded isometric view of the present invention, viewed from above.

FIG. 3 is an exploded isometric view of the present invention viewed from the bottom.

FIG. 4 is a cross-section view taken along lines 4-4 of FIG. 1.

FIG. 5 is a plan section view taken along lines 5-5 in FIG. 4.

FIG. 6 is a plan section view taken along lines 6-6 in FIG. 4.

FIG. 7 is a plan section view taken along lines 77 in FIG. 4.

FIG. 8 is a plan section view taken along lines 8-8 in FIG. 4.

FIG. 9 is a schematic of the electronic circuitry of the present invention.

FIG. 10 is a plan view of the transducer of the present invention.

FIG. 10a is an elevation view of the transducer of the present invention, showing its mode of oscillation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, an isometric view of the assembled sonic signal generator 11, hereafter referred to as a generator, is shown, with the sound limiter ring 12 at the midpoint position between fully open and closed. Acoustic energy in the form of waves is coupled off the transducer 36 mounted inside the generator 11, and subsequently directed through half-covered ports 13 through 16, and others not shown, in such a manner that sound wave cancellation in the composite acoustic wave pattern radiated outwardly from the transducer ports is substantially eliminated.

The generator 11, shown most clearly in the exploded views of FIGS. 2 and 3, comprises five basic parts. A bottom part 18 includes a plate 20, with an integral X-shaped baffle 19 extending therefrom, and an integral housing 30 for receiving an electronic circuit 24. The housing 30 includes three sets of apertures 21-23 to accommodate input connections to the electronic circuit 24.

A first port member 26 is secured on plate 20 of the bottom part 18 by means of protrusions 88-88'and matching receptacles on the first port member 26. The first port member 26 is positioned such that X-baffle 19 is located within the center opening 27 of the port member 26, which opening is defined by an open cylindrical section 31. Each of the free ends 28-28 of the legs 2929 of the X-baffle 19 substantially mate with the interior wall of the open cylindrical section 31.

A conventional transducer 36, comprising a piezoelectric ceramic crystal 28 secured to a thin brass disk 29, is nodally mounted on the free edge 35 of cylindrical section 31. A transducer, as shown in FIG. 10, will flex radially in free space (FIG. 10a) about a particular surface line or path 36a when excited. This path is referred to as the transducers node line, and is determined by the physical configuration of the transducer, e.g., the relative diameters and thicknesses of the brass disk and tlil eefainic crystal.

A top part 34, which is substantially identical to bottom part 18, has a second port member 33, which is identical to first port member 26, secured thereto in a similar orientation and manner as first chamber 26 is secured to the bottom part 18. When the top part -second port member combination is joined to the bottom part-first port member combination by means of protrusions 92-92 and mating receptacles 9393, first and second port members 26 and 33 mate to form a ported closed cylindrical section 48 (FIG. 4) completely enclosing transducer 36. When the first and second port members 26 and 34 are thus mated, the free edge 40 of cylindrical section 34a of second port member 34 extends to nearly touch the surface of transducer 36 along the nodal path on the surface opposite to that of the mounted surface. The free edges 37 and 37a of first and second port members, respectively, terminate at a single plane, forming ports 16 and 14, and others not shown.

When the crystal 28 is electronically excited by the electronic package 24, it begins to flex about its fixed nodal mount. Referring to FIG. a, acoustic waves are coupled off all of the surfaces of the mounted crystal; e.g., the upper surface 49 exterior of the nodal mount 36a, the lower exterior surface 49a, the upper interior surface 49b and the lower interior surface 49c. The acoustic waves coupled off the transducer 36 from the upper interior surface 49b, and lower exterior surface 49a are directed by means of first and second port members 26 and 33 through ports 16 and 13, as will be more fully explained in the following paragraphs, and

also through identical ports (not illustrated) whose radial center lines are displaced at an angle of 180 to the radial center line of ports 16 and 13. Acoustic waves from the upper exterior surface 49 and the lower interior surface 490 are directed through ports 14 and 15, and identical ports whose center lines are 180 removed therefrom, each of which ports is 90 removed from ports 13 and 16 and those 180 degrees removed therefrom. Each of the ports 13-16 and others not shown has a circumferential angle of between 60 and 100. Other port configurations may, of course, be utilized to fit particular applications in accordance with the principles of the invention. For instance, in a particular application, it may be desirable to utilize a single port with wave energy of a single phase .being directed through that port. The structure shown in FIGS. 18 could be easily modified to accommodate such an application, or additional structure could be positioned around the structure of FIGS. 1 and 2 to provide the one-port configuration. Other portions of the apparatus to be explained in more detail in the following paragraphs include the sound limiter ring 12, the separator ring 42, te electronic circuit 24.

A significant part of the generator 11 is the transducer 36, comprised of piezoelectric ceramic crystal 28 and brass disk 29, as is generally shown in the prior art. According to conventional transducer principles, when a ceramic crystalline material is cut and polished in a particular fashion, it will physically distort in response to an electric excitation signal, producing acoustic waves having a frequency dependent upon the physical configuration of the crystalline structure. This frequency may be in a range audible to the human ear. This phenomenon is known as the piezoelectric effect and is utilized in various ways for two-way conversion between acoustic and electric energy.

When excited, the crystal 28 will attempt to expand in a radial direction and the entire transducer element 36 will tend to bend in response thereto. The transducer is conventionally mounted on a circular nodal path 36a some distance inward of the periphery of the disk 29. The transducer is resiliently secured to the free edge 35 of the cylindrical section 31 of first port member 26, and flexes about the nodal path 36a when the transducer is excited. Acoustic waves coupled off the four surface areas 49-49c of the mounted transducer 36 tend to substantially cancel each other if they are otherwise undamped and undirected. Acoustic waves coupled from surface area 49 of transducer 36 and surface area 49c are in phase with each other, as are acoustic waves coupled from surface area 49a and surface area 49b. Acoustic waves from surface areas 49 and 49c are, however, opposite in phase to acoustic waves from surface areas 49a and 49b.

To accomplish the electrical excitation of the transducer 36, an electronic circuit 24 is provided, the output of which is connected to the brass disk 29 and the crystal 28 through connections 43 and 44. A slot 46 in the separator ring 42 guides and secures the connections 43 and 44 from the electronic circuit to the transducer. Referring to FIG. 9, a schematic diagram showing the details of the electronic circuit is shown. Connections 51 and 52 are provided to receive an input signal for energizing the circuit. Applied to connections 51 and 52 may be tip and ring lines of a conventional telephone line pair leading from a central office to an individual receiver unit. Other means of circuit energization may, of course, be utilized and would be obvious to a man skilled in the art. Connection 53 is a ground combination for the circuit, and provides a high impedance circuit for two-party ringing control, to be explained in detail in following paragraphs. It is not required for one-party lines. Typically, in a telephone system application there will be 48 volts DC between connections 51 and 52, and this voltage will normally be blocked by capacitor 54. However, nominal ringing voltage, which may be applied through either connection 51 or 52 from the central office to indicate a call to a particular receiver is volts AC, and this voltage is passed by capacitor 54 to the remainder of the circuit. This 85 volt AC signal is half-wave rectified by diode 56, and the resulting half-wave signal charges capacitor 79 through resistor 58. The charge on capacitor 79 is used to energize drive circuit 59, which includes the transducer 36, connected across the input through transistor 62 and resistor 65.

Resistances 64 and 66 are selected in such a ratio to maintain transistor 63 in a nominal on state, when AC voltage other than prop er ringing voltage, is present between connections 51 and 52. By maintaining transistor 63 in an on condition, transistor 61 is inhibited from operation, and circuit 59 is thus also inhibited from operating. Resistance 60a insures that transistor 61 does not turn on due to leakage current. Circuit 59 is a variation of the drive circuit disclosed in US. Pat. No. 3,742,492 to Proctor, and operates on similar principles. Circuit 59a acts as a variable resistance, and thus connects transducer 36 across the input. One side of transducer 36 is connected to the base of transistor 61. Circuit 59b essentially acts like a programmable unijunction transistor, when allowed to operate by transistor 63. Timing capacitor 57 charges through resistance 60 and this charge builds up until transistor 61 conducts, thereby discharging capacitor 57, and giving a small in-phase voltage boost to transducer 36, and maintaining its excitation.

In operation an 85 VAC ringing voltage will charge capacitor 67 through resistance 68 and diode 69. When the charge on capacitor 67 reaches a value greater than the breakdown voltage of the zener diode 71, current through resistance 64 will be shunted through diode 72 to the other input line and transistor 63 is no longer held in an on state. Circuit 59 is then free to operate as described above at its predetermined frequency.

The circuit shown generally at 73 is also useful in protecting the circuit from inadvertent initiation due to large voltage transients, such as are typically generated by the dialing mechanism of the standard telephone receiver. Diode 69 provides a half-wave rectification of the incoming AC signal, whether it be ringing voltage or transient voltage, passing the positive half cycles to resistance 68. Resistance 68, resistance 74, and capacitor 67 integrate the signal applied from diode 69, and the integrated signal is present at one side of the zener diode 71. If the integrated voltage has a magnitude greater than the breakdown voltage of the zener, the drive circuit 59 will be free to operate, as explained above for the 85 VAC ringing voltage. In the case of large voltage transients, such as encountered in dial receivers, however, the integration function produces a resultant signal having a peak magnitude which is below that of the breakdown voltage of the zener diode, which for purposes of the present invention is approximately 8 volts. Thus, by integrating transient voltage spikes, the drive circuit 59 can be protected from such inadvertent initiation.

Another feature of the circuit of FIG. 9 is the ringing control, generally shown at 76. In some applications, wherein two receivers having different identification numbers are located on the same pair of lines, such as in two-party telephone lines, it is obviously necessary for the system to have the capability of ringing one telephone on the pair without ringing the other. Connecting the circuit of FIG. 9 in a conventional ringer fashion for two-party lines (between one of the lines and ground) would result in a significant amount of 60 cycle noise being introduced into the line, which is undesirable. To provide the ringing control capability, circuit 76 is connected between ground and one line of the pair. Circuit 76 is a high impedance to prevent the introduction of significant 6O cycle noise. FIG. 9 shows aproper operating circuit connection for ringing voltage to be applied through connection 51. If ringing voltage comes in through connection 51, the circuit will function normally, and will provide an audible alarm.

However, if ringing voltage appears on the other line, i.e., through connection 52, the 85 volt AC difference between connection 52 and ground will break down zener diode 77, turn on transistor 78 and discharge capacitor 67 through transistor 78. Since capacitor 67 is thus maintained in a discharge condition, zener diode 71 will not break down, transistor 63 is thus held on and the signal generatorwill not produce an audible alarm. In the other subscribers telephone, connections 51 and 52 are reversed, and the ringing voltage coming in over connector 52 thus will be passed by diode 56 to capacitor 79, powering the oscillator 59, as described above.

Referring now to FIGS. 4 through 6, the ported structure surrounding the transducer, and port member 26 in particular, are shown in detail in section views. With 6 respect to port member 26, a flat, relatively thin ring 81, enclosing opening 27, is provided with an open cylindrical section 31, which is integral at one end thereof with the inner periphery of the ring 81 and which extends perpendicularly from said ring 81. A discontinuous upper wall 82 (FIG. 6) is located on the outer periphery of ring 81 and extends perpendicularly from ring 81 parallel to cylindrical section 31. A discontinuous lower wall 83 (FIG. 5), also located on the outer periphery of ring 81, extends perpendicularly from ring 81 in an opposite direction to that of upper wall 82, with the ends of each portion of the discontinuous lower wall 83 being joined by chord walls 84 and 86 (FIG. 5), which are substantially the same height as discontinuous wall 83. Referring to FIG. 6, the upper wall 82 has a plurality of protrusions 8585 positioned at spaced intervals along the interior surface of the wall 82, which protrusions serve to support the separator ring 42. Connecting the lower wall 83 with chord walls ,mate with surface 44 of plate 20. Transducer 36 is mounted to the free edge 35 of cylindrical section 31, and seals off that end of cylindrical section 31. Acoustic waves coupled off the lower interior surface 490 of the transducer will thus proceed into a first chamber 990 which is formed by the lower interior surface 490 of the transducer, cylindrical section 31, ring 81, plate 20, and chord Walls 84 and 86. The ports 9393 in the first chamber 99a are formed by the discontinuities 93a 93a and sound limiter ring 12 in lower wall 83. Acoustic waves coupled off surface 49c of the trans ducer thus proceed through ports 9393 as shown by the arrows in FIG. 5.

Acoustic waves are coupled off the lower exterior surface 490 of the transducer into a second chamber 99b, formed by the lower exterior transducer surface 49a, separator ring 42, ring 81, cylindrical section 31 and discontinuous wall 82. Acoustic waves coupled off surface 49a thus proceed through ports 9292, formed by discontinuities 92a92a and sound limiter ring 12 as shown by the arrows in FIG. 6.

Referring now to FIGS. 4, 7 and 8, the second port member 33 is shown in some detail in section. When generator 11 is fully assembled, free edge 40 of cylindrical section 340 nearly touches the upper surface of the transducer 36, as explained above. The second port member 34 is identical 'to first port member 26, and comprises a flat, thin ring 101, a cylindrical section 340, discontinuous wall 102 and discontinuous wall 106, with discontinuous wall 106 having the ends thereof joined by chord walls 103 and 104. When port member 33 is secured to top part 34 by protrusions 9797 and mating receptacles 9898, X-shaped baffle is positioned with opening 104a. Referring to FIGS. 4 and 7, acoustic waves are coupled off the upper exterior surface 49 of element 36 into a chamber 99c defined by upper exterior surface 49, separator ring 42, ring 101 of port member 33, cylindrical section 340, and discontinuous wall 102. The acoustic waves proceed outward from chamber 990 through ports 111-111 formed by discontinuities 1lla-ll1u in vertical wall 102 and sound limiter ring 12 as shown by the arrows in FIG. 7.

Referring to FIGS. 4 and 8, acoustic waves are coupled off the upper interior surface 49b of element 36 into a chamber 99d defined by ring 101, cylindrical sec tion 34a, the upper interior surface 49b of transducer 36, plate 94, and chord walls 103 and 104. Acoustic waves flow outward from the chamber through ports 112112 formed by the discontinuities 1l2al12a in wall 106, and sound limiter ring 12, as shown by the arrows in FIG. 8.

Thus, when assembled, the generator 11 directs acoustic waves coupled off the mounted transducer 36 in various radial directions, depending on the phase of the waves, i.e., the surface off which the waves are coupled. Referring again to FIGS. 4-8, acoustic waves coupled off the surface 49c of the transducer flow through ports in the direction shown by the arrows in FIG. 5. Acoustic waves coupled off surface 49 of the transducer, being in phase with that off surface 490, flows in a similar direction, as shown by the arrows in FIG. 7. Acoustic waves from surface 49b of the element will be of opposite phase to that off surface 49 and 49c and its direction is shown by the arrows in FIG. 6. Acoustic waves from surface 49a, being in phase with that from surface 49b, flows through openings in a similar direction, as shown by the arrows in FIG. 8. The entire surface area of the transducer 36 is thus effectively utilized for the production of sound. In testing, it has been shown that directing acoustic waves from the transducer in such a manner produces at least a db increase in sound efficiency.

To control the sound level, a sound limiter ring 12, for purposes of volume control, is provided which is fitted around the periphery of mated port members 26 and 33, the ring 12 being guided by revolving spindle 110 (FIGS. 1-3), which has a circumferential rubber ring 111, pressing lightly against knurled portion 112 of the sound limiter ring 12. The sound limiter ring has plurality of ports which are identical in size and relative location to the ports of the ported structure 48, comprising mated port members 26 and 33. At one position, the ring 12 is coincident with the ports of the mated port members, and all the coupled acoustic waves flow outward from the ported structure. As the ring 12 is revolved, however, the solid portions of the ring begin to cover the ports of port members 26 and 33. At the fully closed position, the solid portions of the sound limiter ring 12 substantially close the ports in port members 26 and 33, thereby substantially decreasing the sound level from the generator 11. FIGS. l-8 show the sound limiter ring 12 at a midpoint or halfopen position.

Thus, a sonic signal generator has been disclosed which utilizes substantially 100 percent of the plane surface area of a nodally mounted piezoelectric transducer for coupling of acoustic waves into an adjacent medium by directing the coupled waves in such a fashion that little or no wave cancellation results. A significant increase in acoustic efficiency is thereby achieved for a given input of power. Volume control means is provided which varies the sound level over a significant range, according to the desire of the user.

Although an exemplary embodiment of the invention has been disclosed herein for purposes of illustration, it should be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

What is claimed is:

1. A sonic signal generator, comprising:

8 transducer means, including a piezoelectric transducing element mounted on a diaphragm, said transducer means having upper and lower surfaces and operative when energized to produce wave energy off said upper and lower surfaces;

means supporting said transducer means along a nodal path of vibration thereof, said transducer means flexing about said nodal path when energized, said upper surface of said transducer means having first central and first peripheral surface portions defined by said nodal path, and said lower surface of said transducer means having second central and second peripheral surface portions defined by said nodal path;

means for energizing said transducer means such that it flexes about said nodal path; and

housing means surrounding said transducer means,

including means routing wave energy from a first one of said first central and first peripheral surface portions and from a second one of said second central and second peripheral surface portions to the atmosphere outside said housing means, sais first and second ones of said first and second central and first and second peripheral surface portions producing in-phase wave energy when said transducing means is energized.

2. The signal generator of claim 1, wherein said first and second central surface portions are substantially equal in surface area, and wherein said first and second peripheral surface portions are substantially equal in surface area.

3. The signal generator of claim 2, wherein wave energy produced off said first central surface portion and said second peripheral surface portions has a first phase, and wherein wave energy produced off said first peripheral surface portion and said second central surface portion has a second phase substantially opposite to that of said first phase.

4. The signal generator of claim 3, wherein said piezoelectric transducing element is a piezoelectric crystal, and said diaphragm is a relatively thin metal disk having two mounting surfaces, said piezoelectric crystal being mounted on one mounting surface of said metal disk.

5. The signal generator of claim 4, wherein said supporting means includes a free continuous edge portion, and wherein said free continuous edge is attached to the other mounting surface of said metal disk along said nodal path of vibration.

6. The signal generator of claim 1, wherein said housing means includes a hollow body having two ends and a peripheral surface extending therebetween, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said two ends, thereby defining defining first and second housing sections.

7. The signal generator of claim 6, including at least one opening defined in each of said first and second housing sections, and wherein said routing means includes means positioned in said first and second housing sections for channeling wave energy produced off said first one of said first central and first peripheral sur ace portions through said opening in said first housingisection and for channeling wave energy produced off said second one of said second central and second peripheral surface portions through said opening in said second housing section.

8. An apparatus in accordance with claim 1, wherein said energizing means includes means operative in response to an input signal to periodically provide a voltage boost to said transducer means, thereby maintaining said transducer means in a state of excitation;

circuit means operative to time-integrate said input signal and to provide an output signal having an amplitude which is the integral of the amplitude of said input signal over time;

means responsive to said output signal for comparing the amplitude of said output signal with a predetermined level of amplitude, and for initiating operation of said energizing means when the amplitude of said output signal is greater than said predetermined level of amplitude.

9. An apparatus of claim 8, wherein said comparing and initiating means includes a zener diode.

10. An apparatus of claim 9, wherein said integrating means includes a parallel connection of a capacitor and resistance means, one end of which parallel connection is electrically coupled to said zener diode.

11. An apparatus of claim 8, wherein said energizing means includes first and second input lines, neither of which are grounded, the input signal to said energizing means appearing on either of said first or second input lines, and wherein said energizing means further includes means connected between one of said first and second input lines and ground, and operative to prevent said energizing means from operating when said input signal is received on a given one of said first and second input lines.

12. An apparatus of claim 11, wherein said preventing means includes means connected to said one end of said capacitor and to said given one of said first and second input-lines to maintain said capacitor in a discharge condition as long as the input signal is present on the given one of said first and second input lines.

13. A sonic signal generator, comprising:

transducer means, including a piezoelectric transducing element mounted on a diaphragm, said transducer means having upper and lower surfaces and operative when energized to produce wave energy off said upper and lower surfaces;

means supporting said transducer means along a nodal path of vibration thereof, said transducer means flexing about said nodal path when energized, said upper surface of said transducer means having first central and first peripheral surface portions defined by said nodal path, and said lower surface of said transducer means having second central and second peripheral surface portions defined by said nodal path;

means for energizing said transducer means such that it flexes about said nodal path; and

housing means surrounding said transducer means,

including first means routing wave energy from a first one of said first and second central and first and second peripheral surface portions to the atmosphere surrounding said housing means in a first direction outward from said housing means, and further including second means routing wave energy from a second one of said first and second central and first and second peripheral portions to the atmosphere surrounding said housing means in a second direction outward from said housing means, said second direction being sufficiently removed from said first direction to substantially reduce interference between wave energy directed in said first and second directions, said first and second ones of said first and second central and first and second peripheral portions producing out-ofphase wave energy.

14. The signal generator of claim 13, wherein said first and second ones of said first and second central and peripheral surface portions are both part of one of said upper and lower surfaces. 7

15. The signal generator of claim 13 wherein said first one of said first and second central and peripheral surface portions is part of one of said upper and lower surfaces, and wherein said second one of said first and second central and peripheral surface portions is part of the other of said upper and lower surfaces.

16. The signal generator of claim 13, wherein said first and second central surface portions are substantially equal in surface area, and wherein said first and second peripheral surface portions are substantially equal in surface area.

17. The signal generator of claim 16, wherein wave energy produced off said first central surface portion and said second peripheral surface portion has a first phase, and wherein wave energy produced off said second peripheral surface portion and said first central surface portion has a second phase substantially opposite to that of said first phase.

18. The signal generator of claim 17, wherein said first routing means includes first means for channeling wave energy produced off said first central surface portion and said first peripheral surface portion through said housing means to the surrounding atmosphere and wherein said second routing means includes second means. for channeling said wave energy produced off said second central surface portion and said second peripheral surface portion through said housing means to the surrounding atmosphere.

19. The signal generator of claim 18, wherein said piezoelectric transducing element is a piezoelectric crystal, and wherein said diaphragm is a relatively thin metal disk having two mounting surfaces, said piezoelectric crystal being mounted on one mounting surface of said metal disk.

20. The signal generator of claim 19, whereinsaid supporting means includes a free continuous edge portion, and wherein said free continuous edge is attached to the other mounting surface of said metal disk along said nodal path of vibration.

21. The signal generator of claim 15, wherein said housing means includes a hollow body having two ends and a peripheral surface extending therebetween, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said two ends, thereby defining first and second housing sections.

22. The signal generator of claim 21 including at least one opening defined in each of said first and second housing sections, and wherein said firs t routing means is positioned in said first housing section and routes wave energy produced off said first one of said first and second central and said first and second peripheral surface portions through said opening in said first housing section, and wherein said second routing means is positioned in said second housing section and routes wave energy produced off said second one of said first and second central and said first and second peripheral surface portions through said opening in said second housing section.

23. The signal generator of claim 18, including a plurality of openings, comprising first and second sets of openings, defined in said housing, said first set of openings being sufficiently spatially removed from said second set of openings to minimize interference between wave energy directed outward from said first and second sets of openings, wherein said first means for channeling includes first and second channels, said first channel connecting said first central surface portion to one of said first set of openings, said second channel connecting said first peripheral surface portion to one of said second set of openings, and wherein said second means for channeling includes third and fourth channels, said third channel connecting said second central surface portion to one of said second set of openings, and said fourth channel connecting said second peripheral surface portion to one of said first set of openings.

24. An apparatus of claim 23, wherein said housing means is a right circular cylinder having closed ends and inner and outer surfaces, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said closed ends, thereby defining first and second cylindrical sections.

25. An apparatus of claim 24, wherein said first channeling means includes a first disk member, and wherein said second channeling means includes a second disk member, said first and second disk members each having defined therein openings located central thereof of approximately the same diameter as said first and second central surface portions, said first and second disk members being positioned transversely of said right circular cylinder at substantially one-quarter and threequarter points along the longitudinal axis thereof, said first and second disk members having inner and outer peripheries, said outer peripheries thereof mating with said inner surface of said right circular cylinder, said first and second disk members further including third and fourth cylindrical sections, respectively, said third and fourth cylindrical sections extending vertically from the inner peripheries of said first and second disk members, and terminating, respectively, at approximately said upper and lower surfaces of said transducer means and coincident with said nodal path of vibration, one of said third and fourth cylindrical sections forming said supporting means, said first and second disk members and said transducer means dividing said right circular cylinder into four substantially longitudinally equal segments, each of said segments having openings defined therein through which wave energy from one and only one of said first and second central and first and second peripheral surface portions is directed to the atmosphere surrounding said housing.

26. An apparatus in accordance with claim 13, wherein said energizing means includes means operative in response to an input signal periodically provide a voltage boost to said transducer means, thereby maintaining said transducer means in a state of excitation;

circuit means operative to time-integrate said input signal and to provide an output signal having an amplitude which is the integral of the amplitude of said input signal over time;

means responsive to said output signal for comparing the amplitude of said output signal with a predetermined level of amplitude, and forr initiating operation of said energizing means when the amplitude of said output signal is greater than said predetermined level of amplitude.

27. An apparatus of claim 26, wherein said comparing and initiating means includes a zener diode.

28. An apparatus of claim 27, wherein said integrating means includes a parallel connection of a capacitor and resistance means, one end of which parallel connection is electrically coupled to said zener diode.

29. An apparatus of claim 26, wherein said energizing means includes first and second input lines, neither of which are grounded, the input signal to said energizing means appearing on either of said first or second input lines, and wherein said energizing means further includes means connected between one of said first and second input lines and ground, and operative to prevent said energizing emans from operating when said input signal is received on a given one of said first and second input lines.

30. An apparatus of claim 29, wherein said preventing means includes means connected to said one end of said capacitor and to said given one of said first and second input lines to maintain said capacitor in a discharge condition as long as the input signal is present on the given one of said first and second input lines.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,921,016

DATED November 18, 1975 INVENTO I David L. Livermore, et al.

It is certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 8, line 23, "sais" should be -said- Column 8, line 56, delete the first occurrence of the word "defining" Column 12, line 19, "forr" should be --.for

Column 12, line 37, "emans" should be --means-- Signed and Sealed this A ttes t:

RUTH C. MASON Arresting Officer C. MARSHALL DANN ('ommissr'uner uj'latems and Trademarks 

1. A sonic signal generator, comprising: transducer means, including a piezoelectric transducing element mounted on a diaphragm, said transducer means having upper and lower surfaces and operative when energized to produce wave energy off said upper and lower surfaces; means supporting said transducer means along a nodal path of vibration thereof, said transducer means flexing about said nodal path when energized, said upper surface of said transducer means having first central and first peripheral surface portions defined by said nodal path, and said lower surface of said transducer means having second central and second peripheral surface portions defined by said nodal path; means for energizing said transducer means such that it flexes about said nodal path; and housing means surrounding said transducer means, including means routing wave energy from a first one of said first central and first peripheral surface portions and from a second one of said second central and second peripheral surface portions to the atmosphere outside said housing means, sais first and second ones of said first and second central and first and second peripheral surface portions producing in-phase wave energy when said transducing means is energized.
 2. The signal generator of claim 1, wherein said first and second central surface portions are substantially equal In surface area, and wherein said first and second peripheral surface portions are substantially equal in surface area.
 3. The signal generator of claim 2, wherein wave energy produced off said first central surface portion and said second peripheral surface portions has a first phase, and wherein wave energy produced off said first peripheral surface portion and said second central surface portion has a second phase substantially opposite to that of said first phase.
 4. The signal generator of claim 3, wherein said piezoelectric transducing element is a piezoelectric crystal, and said diaphragm is a relatively thin metal disk having two mounting surfaces, said piezoelectric crystal being mounted on one mounting surface of said metal disk.
 5. The signal generator of claim 4, wherein said supporting means includes a free continuous edge portion, and wherein said free continuous edge is attached to the other mounting surface of said metal disk along said nodal path of vibration.
 6. The signal generator of claim 1, wherein said housing means includes a hollow body having two ends and a peripheral surface extending therebetween, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said two ends, thereby defining defining first and second housing sections.
 7. The signal generator of claim 6, including at least one opening defined in each of said first and second housing sections, and wherein said routing means includes means positioned in said first and second housing sections for channeling wave energy produced off said first one of said first central and first peripheral surface portions through said opening in said first housing section and for channeling wave energy produced off said second one of said second central and second peripheral surface portions through said opening in said second housing section.
 8. An apparatus in accordance with claim 1, wherein said energizing means includes means operative in response to an input signal to periodically provide a voltage boost to said transducer means, thereby maintaining said transducer means in a state of excitation; circuit means operative to time-integrate said input signal and to provide an output signal having an amplitude which is the integral of the amplitude of said input signal over time; means responsive to said output signal for comparing the amplitude of said output signal with a predetermined level of amplitude, and for initiating operation of said energizing means when the amplitude of said output signal is greater than said predetermined level of amplitude.
 9. An apparatus of claim 8, wherein said comparing and initiating means includes a zener diode.
 10. An apparatus of claim 9, wherein said integrating means includes a parallel connection of a capacitor and resistance means, one end of which parallel connection is electrically coupled to said zener diode.
 11. An apparatus of claim 8, wherein said energizing means includes first and second input lines, neither of which are grounded, the input signal to said energizing means appearing on either of said first or second input lines, and wherein said energizing means further includes means connected between one of said first and second input lines and ground, and operative to prevent said energizing means from operating when said input signal is received on a given one of said first and second input lines.
 12. An apparatus of claim 11, wherein said preventing means includes means connected to said one end of said capacitor and to said given one of said first and second input lines to maintain said capacitor in a discharge condition as long as the input signal is present on the given one of said first and second input lines.
 13. A sonic signal generator, comprising: transducer means, including a piezoelectric transducing element mounted on a diaphragm, said transducer means having upper and lower surfaces and operative when energized to produce wave energy off saId upper and lower surfaces; means supporting said transducer means along a nodal path of vibration thereof, said transducer means flexing about said nodal path when energized, said upper surface of said transducer means having first central and first peripheral surface portions defined by said nodal path, and said lower surface of said transducer means having second central and second peripheral surface portions defined by said nodal path; means for energizing said transducer means such that it flexes about said nodal path; and housing means surrounding said transducer means, including first means routing wave energy from a first one of said first and second central and first and second peripheral surface portions to the atmosphere surrounding said housing means in a first direction outward from said housing means, and further including second means routing wave energy from a second one of said first and second central and first and second peripheral portions to the atmosphere surrounding said housing means in a second direction outward from said housing means, said second direction being sufficiently removed from said first direction to substantially reduce interference between wave energy directed in said first and second directions, said first and second ones of said first and second central and first and second peripheral portions producing out-of-phase wave energy.
 14. The signal generator of claim 13, wherein said first and second ones of said first and second central and peripheral surface portions are both part of one of said upper and lower surfaces.
 15. The signal generator of claim 13 wherein said first one of said first and second central and peripheral surface portions is part of one of said upper and lower surfaces, and wherein said second one of said first and second central and peripheral surface portions is part of the other of said upper and lower surfaces.
 16. The signal generator of claim 13, wherein said first and second central surface portions are substantially equal in surface area, and wherein said first and second peripheral surface portions are substantially equal in surface area.
 17. The signal generator of claim 16, wherein wave energy produced off said first central surface portion and said second peripheral surface portion has a first phase, and wherein wave energy produced off said second peripheral surface portion and said first central surface portion has a second phase substantially opposite to that of said first phase.
 18. The signal generator of claim 17, wherein said first routing means includes first means for channeling wave energy produced off said first central surface portion and said first peripheral surface portion through said housing means to the surrounding atmosphere and wherein said second routing means includes second means for channeling said wave energy produced off said second central surface portion and said second peripheral surface portion through said housing means to the surrounding atmosphere.
 19. The signal generator of claim 18, wherein said piezoelectric transducing element is a piezoelectric crystal, and wherein said diaphragm is a relatively thin metal disk having two mounting surfaces, said piezoelectric crystal being mounted on one mounting surface of said metal disk.
 20. The signal generator of claim 19, wherein said supporting means includes a free continuous edge portion, and wherein said free continuous edge is attached to the other mounting surface of said metal disk along said nodal path of vibration.
 21. The signal generator of claim 15, wherein said housing means includes a hollow body having two ends and a peripheral surface extending therebetween, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said two ends, thereby defining first and second housing sections.
 22. The signal generator of claim 21 including at least one opening defined in each of said first and second housing sections, and wherein said First routing means is positioned in said first housing section and routes wave energy produced off said first one of said first and second central and said first and second peripheral surface portions through said opening in said first housing section, and wherein said second routing means is positioned in said second housing section and routes wave energy produced off said second one of said first and second central and said first and second peripheral surface portions through said opening in said second housing section.
 23. The signal generator of claim 18, including a plurality of openings, comprising first and second sets of openings, defined in said housing, said first set of openings being sufficiently spatially removed from said second set of openings to minimize interference between wave energy directed outward from said first and second sets of openings, wherein said first means for channeling includes first and second channels, said first channel connecting said first central surface portion to one of said first set of openings, said second channel connecting said first peripheral surface portion to one of said second set of openings, and wherein said second means for channeling includes third and fourth channels, said third channel connecting said second central surface portion to one of said second set of openings, and said fourth channel connecting said second peripheral surface portion to one of said first set of openings.
 24. An apparatus of claim 23, wherein said housing means is a right circular cylinder having closed ends and inner and outer surfaces, said transducer means being mounted transversely of said body at approximately a longitudinal midpoint between said closed ends, thereby defining first and second cylindrical sections.
 25. An apparatus of claim 24, wherein said first channeling means includes a first disk member, and wherein said second channeling means includes a second disk member, said first and second disk members each having defined therein openings located central thereof of approximately the same diameter as said first and second central surface portions, said first and second disk members being positioned transversely of said right circular cylinder at substantially one-quarter and three-quarter points along the longitudinal axis thereof, said first and second disk members having inner and outer peripheries, said outer peripheries thereof mating with said inner surface of said right circular cylinder, said first and second disk members further including third and fourth cylindrical sections, respectively, said third and fourth cylindrical sections extending vertically from the inner peripheries of said first and second disk members, and terminating, respectively, at approximately said upper and lower surfaces of said transducer means and coincident with said nodal path of vibration, one of said third and fourth cylindrical sections forming said supporting means, said first and second disk members and said transducer means dividing said right circular cylinder into four substantially longitudinally equal segments, each of said segments having openings defined therein through which wave energy from one and only one of said first and second central and first and second peripheral surface portions is directed to the atmosphere surrounding said housing.
 26. An apparatus in accordance with claim 13, wherein said energizing means includes means operative in response to an input signal periodically provide a voltage boost to said transducer means, thereby maintaining said transducer means in a state of excitation; circuit means operative to time-integrate said input signal and to provide an output signal having an amplitude which is the integral of the amplitude of said input signal over time; means responsive to said output signal for comparing the amplitude of said output signal with a predetermined level of amplitude, and forr initiating operation of said energizing means when the amplitude of said output signal is grEater than said predetermined level of amplitude.
 27. An apparatus of claim 26, wherein said comparing and initiating means includes a zener diode.
 28. An apparatus of claim 27, wherein said integrating means includes a parallel connection of a capacitor and resistance means, one end of which parallel connection is electrically coupled to said zener diode.
 29. An apparatus of claim 26, wherein said energizing means includes first and second input lines, neither of which are grounded, the input signal to said energizing means appearing on either of said first or second input lines, and wherein said energizing means further includes means connected between one of said first and second input lines and ground, and operative to prevent said energizing emans from operating when said input signal is received on a given one of said first and second input lines.
 30. An apparatus of claim 29, wherein said preventing means includes means connected to said one end of said capacitor and to said given one of said first and second input lines to maintain said capacitor in a discharge condition as long as the input signal is present on the given one of said first and second input lines. 